Prior echocardiographic work from our laboratory has demonstrated age-related increases in left ventricular (LV) wall thickness and dimunution of mitral valve closure rate in both men and women, but no alteration in LV chamber size, ejection fraction or velocity of muscle shortening. In order to confirm these cross-sectional observations in a given individual, repeat M-mode echocardiograms are being performed in the men initially studied by our group an average of 6 years ago. Because no direct assessment of diastolic LV function was performed in our earlier studies, we are quantifying rates of LV filling and emptying at rest as well as the rates of ventricular wall thickening and thinning, employing computer digitizing techniques at the Applied Physics Laboratory APL) of Johns Hopkins University. Assessment of cardiac performance during exercise in normal subjects using radionuclide angiocardiography, and two-dimensional echocardiography and assessment of coronary flow via thallium scans will be discussed in an appendix to this report.